An inkjet recording method is rapidly spread and more developed because material cost is low, high-speed recording is feasible, a noise is low while recording is performed, and color recording is easy.
The inkjet recording method includes a continuous manner that continuously disperses a liquid drop and an on-demand manner that disperses a liquid drop according to an image information signal as the inkjet recording method, and a discharging manner includes a manner that discharges a liquid drop by applying pressure by a piezo element, a manner that discharges a liquid drop by generating bubbles in ink by heat, a manner that uses an ultrasonic wave, and a manner that draws a liquid drop by electrostatic force and discharge it. Further, aqueous ink, oily ink, or solid (melt type) ink is used as ink for inkjet recording.
A colorant used in ink for inkjet recording needs to ensure favorable solubility or polydispersity to a solvent, recording at a high concentration, favorable hue, fastness to light, heat, and active gas (NOx, SOx other than oxidative gas such as ozone, or the like) in an environment, excellent fastness to water or chemicals, good fixability to an image-receiving material, low spreading, excellent preservation as ink, non-toxicity, high purity, and availableness at low price. However, it is very difficult to find a colorant satisfying these requirements at a high level.
Particularly, there is a strong demand for an ink composition having a favorable black hue, fastness to light, humidity and heat, a high molar light absorbing coefficient, a high character quality in document printing, and fastness to oxidative gas such as ozone in an environment when printed on an image-receiving material having an ink receiving layer including porous white inorganic pigment particles.
In order to solve the aforementioned problems, Patent Documents 1 and 2 describe an aqueous disazo dye containing two or more heterocyclic rings.
Further, Patent Documents 3 and 4 describe an asymmetric tris or tetrakis azo compound where a benzene ring or a naphthalene ring and a heterocyclic condensed ring are bonded by an azo group as a black colorant providing a black recording image having excellent fastness of an image, particularly, both excellent light resistance and ozone gas resistance.